Rogers Intenet and wireless service was down in southern Ontario and possibly as far as Atlantic Canada for several hours beginning Wednesday evening.
The company acknowledged the problem on its Twitter account.
"Some Rogers customers may be experiencing issues with internet service. We are working to resolve asap and apologize for the inconvenience."
Some angry customers managed to get online anyway and vent their frustration.
Dan Perdue tweeted, "internet is not working and #Rogers tech support lines aren't working...nice...how come their billing system never fails?"
Liam Lahey wrote, "It only took waiting on hold for 52 mins to find out #Rogers DNS server is down from Atlantic Cda to southern Ont. No Internet for a few hrs."
All service was reportedly restored by Thursday morning.
Media reports said Rogers blamed the service outage on damage caused by bad weather.